U.S. Pat. No. 4,887,747 describes a capsule of that type, in which the cover is hinged to the capsule body by means of a stub axle of prismatic cross-section and rotating in bearings constituted by resilient clips. Because of the particular shape of the stub axle, the clips exert a torque on the cover that varies depending on its angular position, and that tends to return it towards its fully-open position and towards its closed position. Making such clips is rather difficult and such a capsule turns out to be complex and expensive to manufacture. In addition, the clips remain visible in all positions of the cover and they leave gaps between themselves and the stub axle, in which gaps bits of cosmetic and other dirt can become trapped, which is undesirable from the point of view of appearance.
French patent application FR-A-2 460 850 discloses a closure capsule in which the cover is connected by a film hinge to a link member secured to the body of the capsule.
During its opening or closing movement, the cover then rubs against a plane region of the body of the capsule.
It is then necessary to exert a relatively large force to bring the cover into its open position.
German utility model DE-U-91 12 615 discloses a closure capsule in which the cover is hinged directly to a member fixed on the receptacle. That capsule requires the use of a special receptacle and also poses problems of sealing and of reliability if the cover is moved beyond its normal opening stroke.